40 THE VOYAGE OF H.M.S. CHALLENGER. 



The first pair of pleopoda in our .specimen, which I believe to be a female, is small 

 and feeble. The four following pairs consist of a long basisal joint supporting two multi- 

 articulate branches, fringed at each margin with long delicately ciliated hairs. The inner 

 branch carries on its inner margin, near its base, a single straight stylamblys. 



The sixth pair of pleopoda forms the lateral plates of the rhipidura or tailpiece, 

 and consists of a short peduncle and two large subecpially broad and long plates, each 

 having a small tooth near the outer terminal angle, while the posterior margin is fringed 

 with a row of long ciliated hairs deeply implanted in the edge. 



The branchial apparatus consists of tolerably well-developed mastigobranchise, to 

 which a podobranchial plume is attached, excepting the penultimate pair of pereiopoda, 

 where the mastigobranehial plate exists in a well-developed condition, without any 

 branchial plume. The plumes generally consist of a stem, with two rows of cylindrical 

 filaments. These may be formulated as follows : — 



Pleurobrancbise, . . . ..'. 



Arthrobranchiae, . . . ... 2 2 2 2 2 



Pod.obrancb.ise, 



Mastigobrancbise, 



Eiconaxius, n. gen. 



Characters generally resembling Axius. First somite of the pleon shorter than the 

 second. Second pair of antennae having the peduncle furnished with a scaphocerite and 

 stylocerite. 



This genus differs from Paraxius in having both scaphocerite and stylocerite, which 

 are absent in that genus ; this character also separates it from Axius, which has a small 

 scaphocerite only. The stylocerite, which is present in this genus, is wanting in Axius, 

 as it is in all the Macrura, except Eiconaxius and Cheiroplatea. Its presence is a feature 

 most prevalent in the Anomurous Crustacea. 



Geographical Distribution. — We only know this genus as an inhabitant of the 

 Celebes Seas, and of the Pacific Ocean near the Kefmadec Islands. 



Eiconaxius acutifrons (PI. V. fig. 2, d-q). 



Rostrum dorsally flattened and sharp pointed ; narrow in the male, broad, and a little 

 horter in the female. First pair of pereiopoda with the right and left propoda subequal 

 in the male, and ecpial in the female ; compressed laterally and very deep, deeper at the 

 posterior margin than the carpos ; pollex armed on the inner side with a long, smooth, 

 depressed tubercle, and the incisive margin beyond slightly serrated. Dactylos broad, 

 deep, arched, and pointed, armed with a strong smooth convex tubercle near the base. 



s 



